The invention is based on a method for sterilizing product-carrying parts of a packaging machine, as generically defined hereinafter.
In packaging systems for aseptic package filling, parts that come into contact with the filling product or with the packaging material must not come into contact with unsterile articles or the ambient air again after the sterilizing phase that precedes the filling phase, so as to avoid reinfection. In a method known from EP A 232 943, which is performed in a packaging machine with two coaxial filling tubes, this requirement is met by using the inner filling tube to deliver the sterilizing agent, such as steam, and the outer filling tube to remove it; a connecting plate inserted into the outlet opening of the outer filling tube diverts the sterilizing agent, flowing in through the inner filling tube, into the protruding outer filling tube. After sterilization of the filling tubes and after a support cap for the connecting plate has been removed, the tube of packaging material is slipped over the filling tube ends and its end is closed with a sealed seam. The connecting plate is then pushed out of the opening of the outer filling tube into the end portion of the tube of packaging material, by a valve rod that passes through the inner filling tube; the connecting plate is sealed in at that end of the tube of packaging material, and at the same time a new end portion of tubular packaging material is formed with a sealed seam. After the partitioned-off end portion of the tube of packaging material has been severed from the remainder of the tube of packaging material, then the tubular end segment, which surrounds the filling tubes, and the outer walls of the filling tubes are acted upon by a sterilizing agent for a predetermined length of time, and the filling operation is then begun.
A disadvantage of this known method is that performing it requires two coaxial filling tubes and one externally actuatable rod for pushing off the connecting plate. There is a need for a sterilizing method for packaging machines of the type referred to at the outset that has only one filling tube that enters the tube of packaging material.